Summary Leukemia inhibitory factor (LIF) is an anti-inflammatory cytokine that activates the expression of endogenous antioxidants in neural cells. Our laboratory has been examining the efficacy of LIF in the rodent stroke model of middle cerebral artery occlusion (MCAO), which reflects the most commonly occluded vessel in humans. We have found that LIF administered at 6 h after MCAO improves anatomical and functional outcomes in rats. Of interest, this treatment reflects a 33% extension of the therapeutic window when extrapolated to the current clinical stroke window for therapy. LIF increased the expression of antioxidant proteins via Akt in cultured neurons and oligodendrocytes. Aim 1: Is the efficacy of LIF dependent on SOD? We have found total superoxide dismutase (SOD) levels are significantly elevated and protein levels of one isoform, SOD3, are increased several-fold at 3 days following MCAO. In this Aim, we will determine if specific SOD subtype(s) are responsible for the LIF-induced effects and determine cell-specific expression of these SOD isoforms. MCAO studies will first use knockout mice to examine the SOD subtypes and these results will then be confirmed in rats. Aim 2: Does this LIF dosing regimen translate into long-term behavioral recovery? This Aim will determine whether this treatment regimen has lasting effects. These data will be used to devise a treatment regimen to extend the short-term efficacy to long-term histological and functional recovery at 90 days post-MCAO in rats. Aim 3: Which signals are transduced following LIF activation? The efficacy of LIF is dependent on the protein kinase Akt. From analysis of antioxidant promoters, the transcription factor MZF-1 is the putative transcription factor that activates their gene expression via Akt. We will use immunohistochemistry and gel shift assays to quantify their expression and promoter binding, respectively, in the infarct regions of rats treated with LIF after MCAO. siRNA techniques with neuronal cultures will be employed to knock down expression of this factor to validate previous findings. Aim 4: Will LIF administration be effective in elderly rats after MCAO? In this Aim, we will treat elderly male and female rats in short-term studies. These studies will be used to determine if there are any age- or sex- dependent differences in LIF efficacy after MCAO. Both histological and functional recovery will be examined. This proposal is aimed to further elucidate the mechanism(s) of LIF treatment and optimize the treatment regimen for long-term efficacy. While treatment with exogenous antioxidants has failed, we believe that the systemic activation of endogenous antioxidants is a better approach and could have substantial implications for treating clinical stroke.